I put the private IP on eth0:0 (that's what the Network settings tab in the manager says to do). It looks really odd, and I haven't changed any firewall rules for it yet. I don't do anything production at Linode (yet).
So in Ubuntu/Debian, /etc/network/interfaces, I've got:
Code:
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet static
address <PUBLIC_IP>
netmask 255.255.255.0
gateway <GATEWAY>
auto eth0:0
iface eth0:0 inet static
address <PRIVATE_IP>
netmask 255.255.128.0
I only got as far as restarting the network and pinging that private IP...